1. Field of the Invention
The present invention relates to an electromagnetic contactor, and more particularly, to an electromagnetic contactor including a ‘b’ contact switch at a coil circuit portion.
2. Background of the Invention
Generally, a direct current relay or an electromagnetic contactor is a type of electrical circuit switching device for performing a mechanical driving and transmitting a current signal using an electromagnet. The direct current relay or electromagnetic contactor is installed at various types of industrial equipment, machines, vehicles, etc.
The electromagnetic contactor may include a main contact mechanism for performing power supply to a load or disconnecting power supply to the load, and an auxiliary contact mechanism for performing power supply to a magnetic coil of the main contact mechanism or disconnecting power supply to the magnetic coil of the main contact mechanism.
FIG. 1 is an exploded perspective view of an electromagnetic contactor in accordance with the conventional art. FIG. 2 is a perspective view of a movable core of FIG. 1. FIG. 3 is a perspective view illustrating a state where a movable core of FIG. 1 is inserted into a bobbin. FIG. 4 is a longitudinal sectional view of an electromagnetic contactor in accordance with the conventional art.
As shown, the conventional electromagnetic contactor includes a lower frame 110, a bobbin 120, a spring 130, a movable core 140, a holder assembly 150, an upper frame 160, etc.
The upper frame 160 and the lower frame 110 are detachably assembled to each other, and form an accommodation space therein so as to accommodate the bobbin 120, the spring 130, the movable core 140, the holder assembly 150, etc.
The holder assembly 150 is provided with movable contacts 151 for respective phases. If the holder assembly 150 is downward moved, the movable contact 151 comes in contact with a fixed contact 152 installed at the bobbin 120. As a result, a current flows to a load side from a power side.
The movable core 140 includes a body portion 141 having a cylindrical shape, a movable core plate 142 coupled to an upper part of the body portion 141, and a coupling plate 144 coupled to an upper surface of the movable core plate 142. An extension portion 143 protrudes from a front surface of the movable core plate 142, and a switch manipulation protrusion 145 is provided on a lower surface of the extension portion 143.
The movable core 140 is inserted into the bobbin 120 so as to be movable up and down. When a magnetic field is applied to a coil 129, the movable core 140 moves downward by a magnetic force. Since the movable core 140 is in a coupled state to the holder assembly 150, it pulls the holder assembly 150 downward while performing a downward motion.
A fixed core 121 is installed at a core insertion portion 122 of the bobbin 120. A printed circuit board (PCB) 126 is provided on a front surface of the bobbin 120, and a ‘b’ contact switch 127 is installed at the PCB 126.
When a switch lever 128 is in an upwardly-moved state, the ‘b’ contact switch 127 connects an external power to the coil 129 to form a magnetic field at the coil 129. On the other hand, when the switch lever 128 is in a downwardly-moved state, the ‘b’ contact switch 127 makes an external power not be connected to the coil 120. In order for the movable core 140 to be moved downward, a large force is required initially. Accordingly, the movable core 140 is pulled by using a magnetic force of the coil 129. In a normal state, a magnetic force of the coil 129 may be removed, because a coupled state between the movable core 140 and the fixed core 121 is maintained by a sustained current. Accordingly, it is preferable to cut off an external power transmitted to the coil 129, as a switch manipulation protrusion 145 presses the switch lever 128 of the ‘b’ contact switch 127 after the movable core 140 has been moved downward.
However, in the conventional electromagnetic contactor, abrasion and damage occur due to repeated collisions between the switch manipulation protrusion 145 and the switch lever 128.